[Staowners] SCUTTLE SHAKE REVISITED

[terry poole]

I agree!

Simple then - buy some round tyres and get your wheels balanced  
properly.

What a relief!

Terry.
On 12 May 2008, at 15:35, CotaLymepond at aol.com wrote:

> Ah  Heck ... here's my 5 cents worth
>  Scuttle shake is when we see the front portion of our cars vibrate.  
> (if you really want to experience this phenomenon, go for a ride in  
> an old T-series MG)  The body on a roadster is somewhat flexible by  
> design, throw in 60 years of wear and tear, a little rust, and  
> squashed out body mounts and the cowl (American-ese for scuttle)  
> will certainly shake around a bit. This is to be expected on a rough  
> road, However if this problem is experienced on smooth flat  
> pavement, and only at a certain speed then it has to be a result of  
> harmonics, a magnification of vibrations from a rotating mass, most  
> likely the wheels and tires, or an out of balance driveshaft. If  
> running the car up on blocks doesn't duplicate the problem then the  
> imbalance is probably in the front wheels. (although if the rear  
> axle is sitting on jackstands, then an imbalance in the rear might  
> not gain resonance as the flexibility of the tires would allow the  
> axle to vibrate, whereas the axle sitting firmly on stands would  
> prevent the harmonics from getting started and building on itself.)
> The reason sedans don't experience this is because the roof  
> structure ties the cowl into the rest of the body and the whole body  
> would have to shake as one unit, which would not seem as evident  
> from  the drivers seat.  If the problem was related to the engine  
> shaking through the motor mounts, then the problem would be evident  
> at certain engine RPM's, regardless of the vehicle's speed.
> It seems that the most likely cause is an out of balance tire, or a  
> bent wheel, or just an out of round tire, (very common on belted  
> tires, even when they're new) I would be willing to bet that if one  
> of these cars with severe scuttle shake was fitted with a set of new  
> balanced radial tires, the problem would go away?
> Just my thoughts <> Steve Cota <>
>
>
>
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